A conventional housing-type pipe joint 100H is shown in FIG. 13. This housing-type pipe joint integrally couples two pipes in the following manner. Pipe ends of pipes 150, 150 having circumferential grooves 151, 151 in pipe end portions are set to abut on each other concentrically, an annular elastic seal ring 102 is fit around an outer side of their joint portion, thereafter a pair of substantially semi-circular joint segments 101, 101 are put on the pipe end portions via the elastic seal ring 102 so that convex strips 113, 113 formed in inner peripheral surfaces of the joint segments 101, 101 are fit in the circumferential grooves 151, 151, and fastening elements composed of bolts 103, 103 and nuts 104, 104 are screwed to bolt insertion holes 121, 121 provided in facing flange portions 120, 120 of the joint segments 101, 101.
Further, in this coupling, as the facing flange portions 120, 120 of the pair of joint segments 101, 101 are made to approach each other by the fastening elements 103, 104, the joint segments 101, 101 are bent so that radii of curvature thereof become smaller, and peripheral edges 114, 114 of the joint segments 101, 101 press and hold pipe outer surfaces (in the shown example, they are bottoms of the circumferential grooves 151 but this is not restrictive) 152, 152, whereby deviation displacement of axes of the both pipes is prevented.
In this coupling, it is confirmed that the coupling by the housing-type pipe joint 100H is completed, when the whole ranges of the peripheral edges 114, 114 of the joint segments 101, 101 match the pipe outer surfaces 152, 152 or when a tightening torque becomes equal to a value pre-designated by using a torque wrench.
However, in coupling the pipes by the housing-type pipe joint 100H, for example, even though the deviation movement of the pipe axes of the pipes 150, 150 is prevented by the peripheral edges 114, 114, it is only necessary that this movement of the aforesaid pipes is sufficiently restricted by the housing-type pipe joint 100H, and the whole ranges of the peripheral edges 114, 114 need not match the pipe outer peripheral surfaces 152, 152.
In the conventional housing-type pipe joint 100H, an appropriate fastening degree is not known, that is, it is not known to what degree the joint segments 101, 101 should be bent and to what degree of ranges the peripheral edges 114, 114 should match the pipe outer surfaces 152, 152 in order for the coupling function to be sufficiently exhibited, and as a result, the facing flange portions 120, 120 of the joint segments 101, 101 have to be made to approach each other until the whole ranges of the peripheral edges 114, 114 match the pipe outer surfaces 152, 152, that is, until the joint segments 101, 101 bend to the largest possible degree, which requires an extremely troublesome and useless operation.
Further, the designation of the tightening torque by the trench wrench requires a troublesome operation such as a need for preparing the trench wrench though being capable of achieving accurate fastening.
Further, attaching such a conventional housing-type pipe joint 100H requires very troublesome operations such as once removing the bolts 103, 103 and the nuts 104, 104 from the flange portions 120, 120 of the joint segments 101, 101, putting the annular elastic seal ring 102 on the joint portion, then fitting the joint segments 101, 101 on the outer side of the elastic seal ring 102 while visually confirming that the stopper pieces 113, 113 are fit in the circumferential grooves, inserting the bolts 103, 103 again through the bolt insertion holes 121, 121 of the facing flange portions 120, 120, and screwing the nuts 104, 104 to the bolts 103, 103.